Laminated roof construction

ABSTRACT

A roof construction comprised of a shell having a hyperbolic paraboloid configuration defined by a pair of superimposed plywood layers, each layer being comprised of a plurality of substantially flat plywood segments joined together at contiguous surfaces to form two sets of joints. In each layer the joints of one set are perpendicularly disposed to the joints of the other set, and each set of joints in one layer is substantially parallel to, and laterally offset from a corresponding set of joints in the other layer. Edge beams are joined to the shell about the outer periphery thereof, and are supported by diametrically opposed buttresses.

U ite et a1.

States Patet [541 LAMINATED ROOF CONSTRUCTION [72] Inventors: Solomon Kirschen, 1727 Danford Street,

Philadelphia, Pa. 19152 [22] Filed: Nov. 18, 1969 [21] Appl.No.: 877,605

[451 Apr.4,1l972 OTHER PUBLICATIONS Materials and Methods- Pgs. 178 & 179- Aug. 1960 P/A Primary Examiner-Henry C. Sutherland Att0rneyKarl L. Spivak [5 7] ABSTRACT A roof construction comprised of a shell having a hyperbolic paraboloid configuration defined by a pair of superimposed plywood layers, each layer being comprised of a plurality of substantially fiat plywood segments joined together at contiguous surfaces to form two sets of joints. In each layer the joints of one set are perpendicularly disposed to the joints of the other set, and each set of joints in one layer is substantially parallel to, and laterally offset from a corresponding set of joints in the other layer. Edge beams are joined to the shell about the outer periphery thereof, and are supported by diametrically opposed buttresses.

3 Claims, 4 Drawing Figures PATENTEDAPR 4 m2 26 INVENTOR. 22 SOLOMON KIRSCHEN ATTORNEY.

LAMINATED ROOF CONSTRUCTION BACKGROUND OF THE INVENTION This invention relates to roof constructions having a shell of a hyperbolic paraboloid configuration, and more particularly to roof constructions in which the shell is comprised of laminated layers, each layer being constructed of a plurality of segments joined together at contiguous surfaces.

Roof constructions having a hyperbolic paraboloid construction are well known in the prior art. As is also well know, the hyperbolic paraboloid type of construction makes efficient use of materials by relying on form or shape for strength rather than on mass or depth of bending members. Such a construction has a double curvature which enables loads to be transferred to supports entirely by direct forces so that all material in the cross-section of the roof is uniformly stressed.

Most prior art hyperbolic paraboloid shells in roof constructions require complete on site fabrication and cannot be prefabricated in smaller sections of the shell for shipment to the building site. For applications requiring relatively short roof spans, such as in housing units and other small buildings, the prefabrication of shells would be advantageous.

Roof constructions of reinforced concrete or similar material require the use of pans or forms for supporting the construction until it sets sufficiently to be self-supporting, at which time the forms must be removed. The fabrication of such concrete structures requires expensive materials and highly skilled labor. Also the removal of the forms from the roof construction must be done with extreme caution to avoid dropping the forms and thereby possibly injuring others working in the area. Additionally, the fabrication of the forms and their subsequent removal after the concrete curing period all contribute significantly to the cost of construction.

The exposed surface of many prior art roof constructions are unsightly and therefore require finishing operations to improve the finished appearance. In many instances a separate interior ceiling is provided to cover such surfaces and quite often, elaborate insulating techniques are required.

SUMMARY OF THE INVENTION The roof construction of the present invention has a shell of a hyperbolic paraboloid configuration, the said shell comprising a pair of laminated plywood layers. Each plywood layer is made up of a plurality of plywood segments which are joined together in edge to edge juxtaposition along contiguous edge surfaces thereof to form respective sets of joints in each layer. The joints of one set are substantially perpendicular to the joints of the other set and each set ofjoints in one layer is substantially parallel to, and laterally offset from a corresponding set ofjoints in the other layer.

Since the shell is comprised of individual plywood segments of the readily available 4-foot by 8-foot size which can be readily spliced or joined to each other, the shell can be prefabricated and shipped to the building site in sections and finally assembled thereat. Since the shell is manufactured of plywood, the need for steel reinforcement and concrete are eliminated, thereby resulting in considerable savings both in construction costs and in the time period required to complete the construction operations.

One plywood layer is manufactured by utilizing a falsework having a hyperbolic paraboloid configuration, and this layer serves as the basic framework to which a second ply is laminated. Thus, the basic framework becomes an integral part of the final shell structure, and the need for separate, removable pans or forms at the building site is eliminated. Since the construction lends itself to prefabrication, the falsework need not be at the building site and can be designed for reuse to provide considerable cost savings.

Once the shell dimensions are established, the various pieces oflaminating material can be mass produced for many shell roofs of the same size. Therefore, the roof construction of this invention can be produced more economically than roof constructions requiring complete fabrication at the job site.

The roof construction of this invention eliminates the need for many different trades, requiring only carpenters to assemble it.

If the bottom layer of the shell is neatly laid, separate ceilings or other finishing operations will not be required and the bottom layer can thus conveniently serve as the finished ceiling.

The laminated construction of this invention eliminates the need for varied type of fastening methods and devices which are required to manufacture prior art constructions.

Other objects and advantages, as well as a fuller understanding of the invention will be had by referring to the following description and claims of a preferred embodiment thereof taken in conjunction with the accompanying drawing wherein like reference characters refer to similar parts throughout the several views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the roof construction of this invention.

FIG. 2 is an end elevation view taken along line 2-2 ofFIG. 1, looking in the direction of the arrows.

FIG. 3 is a top plan view of FIG. 1, partially broken away to show the laminar construction.

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3, looking in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENT Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of my invention selected for illustration in the drawings and are not intended to define or limit the scope of the invention.

Referring to FIG. 1, the roof construction 10 of this invention is shown as comprising a shell 12 of hyperbolic paraboloid configuration ll, edge supports l4, 16, 18, 20 and a pair of opposed supporting buttresses 24, 24.

The shell 12 is fabricated to the form of a hyperbolic paraboloid, which is one of the types of construction that makes efficient use of materials by relying on form or shape for strength, rather than on mass or depth of bending members. Hyperbolic paraboloid constructions are well known, and for a full discussion of the theoretical aspects of such constructions, reference may be made to PORTLAND CEMENT ASSOCIATION, ST Elementary Analysis of Hyperbolic Paraboloid Shell, 1960, which is hereby incorporated by reference.

A hyperbolic paraboloid is a double curvature structure which enables loads to be transferred to supports entirely by direct stresses, rather than through bending, whereby the construction materials are uniformly stressed parallel to the surface. In accordance with established theory of hyperbolic paraboloid construction, relatively low stresses result in the shell 12. This is because the shell consists of a series of parallel parabolas in each of the two diagonal directions 26, 28 (FIG. 3) and parabolas are the most efficient axially stressed shape for arch construction. At an angle of 45 to the diagonals 26, 28 (for a square plan), the shell is defined by a plurality of straight lines. Each line at an angle of 45 to each of said diagonals is progressively rotated with respect to an adjacent and parallel line about an axis which is common and perpendicular to said adjacent and parallel lines. (See FIG. 2). Horizontal sections through the shell form hyperbolic curves parallel to each other. Because a hyperbolic paraboloid is defined by a series of straight lines it is easily constructed by utilizing a falsework or support consisting of straight line supports.

Referring in particular to FIGS. 1, 3 and 4, the construction of shell 12 will now be described. The shell 12 is comprised of an upper plywood layer 30 and a lower plywood layer 32, said layers being laminated to each other with glue, nails, staples or a combination thereof.

The upper plywood layer 30 is constructed of a plurality of plywood segments 34 which are preferably rectangular in plan view and which are spliced or joined to adjacent segments along contiguous edges by glue or the like to define a plurality of parallel spaced joints 36, 38. Joints 36 are substantially perpendicular to the joints 38.

The lower plywood layer 32 is similarly constructed of plywood segments 40 which are preferably identical to segments 34. The longer dimension of segments 40 are disposed substantially perpendicular to the longer dimension of segments 34, it being understood that all segments comprising a given layer are disposed with their longer dimension in the same direction. The plywood segments 40 are joined to adjacent segments at contiguous edge surfaces by glue or the like to define a plurality of parallel joints 42, 44, the joints 42 being substantially perpendicular to the joints 44. The joints 42 are substantially parallel to and laterally offset from the joints 36 and the joints 44 are substantially parallel to and laterally offset from the joints 38. This staggered arrangement of joints allows the stress in either layer to be carried to the other layer through the mutual contact surface 46 (FIG. 4) when such stress encounters a joint. Therefore, each layer 30, 32 should be designed of a thickness to carry the full stress in the shell. in one embodiment of the invention the particular dimensions of the plywood segments 34, 40, are 4 feet by 8 feet by five/sixteenths inches; it being understood that these dimensions will vary depending on design specifications and local building codes.

The edge supports 14, 16, 18, 20 surround the periphery of the shell 12 and are preferably joined thereto by glue, nails, staples, or a combination thereof in well-known manner and are preferably manufactured of sized lumber. The edge support 14 (FIG. 4) is comprised of two separate cooperating support members 14a and 14b. Member 140 is joined to the upper surface of the plywood layer 30 and the member 1412 is joined to the lower surface of the plywood layer 32; the members 14a and 14b are respectively arranged in the same vertical plane. The edge supports 16, 18, 20 are identical to the edge support 14. The edge supports join to the diametrically opposed supporting buttresses 22, 24 to complete the roof construction of this invention; the load supported by the shell being transmitted through the edge supports to the supporting butresses.

Referring to FIG. 3, the quadrants A, B, C, D, defined by dashed lines 48, 50 each constitute a hyperbolic paraboloid construction, and it is within the scope of this invention to rearrange the quadrants, edge supports and buttresses to provide other roof profiles.

The dimensions of the various elements of this invention will depend upon the particular application of the roof construction and the requirements of local building codes.

The glue utilized at the contact surfaces may be either exterior or interior type depending upon the exposure of the structure. When the equilibrium moisture content of the beam in use does not exceed 18 percent, the glue may be casein type containing a mold inhibitor and conforming with Federal Specification MMM-A-l25. When the equilibrium content of the beam exceeds 18 percent, the glue may be ofa room or intermediate temperature setting resin adhesive conforming with Military Specification MlL-A-397B. Phenol, resorcinol or melamine base adhesives are exemplary of suitable resin adhesives.

1 claim:

1. In a load carrying roof construction of hyperbolic paraboloid configuration wherein a shell of desired peripheral configuration is defined by a series of first parallel parabolas in a first diagonal direction and by a series of second parallel parabolas in a second diagonal direction, wherein the said first diagonal direction is disposed at from the second diagonal direction and wherein the roof load is carried by spaced supporting means, the combination of A. a plurality of first rectangular segments arranged in edge to edge juxtaposition to define a first layer of the shell and to provide a plurality of contiguous edges, 1. said contiguous edges being oined together to define a plurality of parallel, spaced first and second joints,

a. said first joints being perpendicular to the second joints,

b. said first and second joints respectively positioning at an angle of 45 from the said first and second parallel parabolas,

c. said first joints of adjacent first rectangular segments aligning to define a plurality of first straight lines,

.1. each said first straight line angularly inclining with respect to each other first straight line,

d. said second joints of adjacent first rectangular segments aligning to define a plurality of second straight lines,

.1. said second straight lines being disposed at an angle of 90 from the second straight lines,

.2. each said second straight line angularly inclining with respect to each other said second straight line;

B. a plurality of second segments arranged in surface to surface contact with the first rectangular segments,

1. said second segments holding the first rectangular segments in said edge to edge juxtaposition,

2. said second segments defining a second layer of the shell,

a. said second layer being in vertical registry with the first layer; and

C. edge supports surrounding the shell at the periphery thereof,

1. said edge supports being secured to the first and second segment portions forming the outer periphery of the shell,

2. said edge supports transmitting the load carried by the shell to the spaced supporting means.

2. The invention of claim 1 wherein the second segments are joined together to form a plurality of first and second joints, the said first joints being perpendicular to the second joints.

3. The invention of claim 2 wherein the first joints of the second layer are substantially perpendicular to the said first joints of the first layer and are laterally offset from the second joints of the first layer. 

1. In a load carrying roof construction of hyperbolic paraboloid configuration wherein a shell of desired peripheral configuration is defined by a series of first parallel parabolas in a first diagonal direction and by a series of second parallel parabolas in a second diagonal direction, wherein the said first diagonal direction is disposed at 90* from the second diagonal direction and wherein the roof load is carried by spaced supporting means, the combination of A. a plurality of first rectangular segments arranged in edge to edge juxtaposition to define a first layer of the shell and to provide a plurality of contiguous edges,
 1. said contiguous edges being joined together to define a plurality of parallel, spaced first and second joints, a. said first joints being perpendicular to the second joints, b. said first and second joints respectively positioning at an angle of 45* from the said first and second parallel parabolas, c. said first joints of adjacent first rectangular segments aligning to define a plurality of first straight lines, .1. each said first straight line angularly inclining with respect to each other first straight line, d. said second joints of adjacent first rectangular segments aligning to define a plurality of second straight lines, .1. said second straight lines being disposed at an angle of 90* from the second straight lines, .2. each said second straight line angularly inclining with respect to each other said second straight line; B. a plurality of second segments arranged in surface to surface contact with the first rectangular segments,
 1. said second segments holding the first rectangular segments in said edge to edge juxtaposition,
 2. said second segments defining a second layer of the shell, a. said second layer being in vertical registry with the first layer; and C. edge supports surrounding the shell at the periphery thereof,
 1. said edge supports being secured to the first and second segment portions forming the outer periphery of the shell,
 2. said edge supports transmitting the load carried by the shell to the spaced supporting means.
 2. said second segments defining a second layer of the shell, a. said second layer being in vertical registry with the first layer; and C. edge supports surrounding the shell at the periphery thereof,
 2. said edge supports transmitting the load carried by the shell to the spaced supporting means.
 2. The invention of claim 1 wherein the second segments are joined together to form a plurality of first and second joints, the said first joints being perpendicular to the second joints.
 3. The invention of claim 2 wherein the first joints of the second layer are substantially perpendicular to the said first joints of the first layer and are laterally offset from the second joints of the first layer. 